Two more candidates have entered the race to fill retiring GOP Rep. Tom Petri’s House seat in Wisconsin. Republican state Senator Joe Leibham said Tuesday afternoon that he will join the race for the GOP nomination.

Earlier on Tuesday, Winnebago County Executive Mark Harris became the first Democrat to announce his candidacy , telling Oshkosh Northwestern Media he is a “fiscally conservative progressive.” Harris faces an uphill climb in this Republican district. The Rothenberg Political Report/Roll Call rates this race as a Safe Republican contest, and whoever wins the GOP primary in August will likely win the general election in November.

Some Wisconsin strategists have predicted Leibham could be the front-runner in the GOP primary because his state Senate district encompasses much of the 6th District and he is well known in the area.

State Sen. Glenn Grothman and state Rep. Duey Stroebel have already jumped into the GOP primary race. John Hiller, an adviser to Gov. Scott Walker, is also considering a run.